The invention relates to a diaphragm of a diaphragm press for separating liquid and solid materials by action of a flowable pressure medium on the materials via the diaphragm, which is fastened in a pressing vessel of the press and divides this pressing vessel into a pressure chamber and a press chamber.
A membrane (also called a diaphragm) of a press intended for separating liquid and solid materials is known from Swiss Patent Application CH-A 686 93 (Bucher-Guyer). This membrane is fastened in a cylindrical pressing vessel of the press between a pressure chamber and a press chamber, parallel to the cylinder axis. The membrane is shaped in tub-like fashion and comprises two semicircular membrane parts, oriented toward the face ends of the pressing vessel, and one middle part, connected to the other two parts on both sides and corresponding to approximately half of the jacket of the vessel.
The membrane parts are built up from a fabric coated with plastic on both sides. The semicircular membrane parts are divided up into segments, and the filament systems of the fabric in each segment are oriented parallel to the radially extending bisector of the respective segment. This achieves improved dimensional stability in the radial main loading directions and prevents destruction of the connection between the fabric and the coating.
However, the service life of such known membranes is not satisfactory and is a primary reason for the only limited spread of the membrane presses in question. The membrane material used is a polyester fabric coated on both sides with a cross-linked polyurethane. It is the action of drainage elements suspended from the membranes that has a substantial influence on the service life of the membranes. In retraction processes of the membrane in the press under a vacuum and when the material being pressed is loosened up, major forces are introduced to the membrane via these drainage elements. These forces lead to severe tensile and shear stresses.
Damage patterns of membranes show a separation of the coating from the fabric, with bubbles being formed. As soon as one of the bubbles pops, the membrane becomes leaky and must then be repaired or replaced entirely.
The object of the invention is to overcome these disadvantages of the known membranes by means of a novel embodiment.
According to the invention, this object is attained in a diaphragm of the type defined at the outset by a dual embodiment comprising two parts, both of which extend over the entire diaphragm area and are solidly connected to one another at only a number of separate connection points on the diaphragm area, and of which one part has essentially only a sealing function, while the other part has essentially only a retention function.
The diaphragm is preferably embodied such that the part with the sealing function is disposed toward the press chamber, and the part with the retention function is disposed toward the pressure chamber, and that at the separate connection points of these parts, connecting elements are provided, which have means for anchoring flexible, ropelike drainage elements, which extend through the press chamber between the diaphragm and a jacket of the pressing vessel of the press. Advantageously, the part having the sealing function is embodied as a cloth of homogeneous rubber or cross-linked polyurethane, with a thickness adequate for the requisite stability, and that the part having the retention function is embodied as a cloth of gas-permeable, non-coated high-strength woven polyamide fabric. The part having the retention function includes a multiaxial filament cluster or network of a plurality of filament systems.
Further variants of the diaphragm are defined by the claims.